He sparked mass treasure hunts across California after hiding hundred dollar bills in envelopes and posting online cryptic clues to their location under the Twitter handle HiddenCash.
But the donor remained anonymous, saying only that he was a member of the "one per cent" of richest Americans who wanted to "pay it forward" and share his wealth with others.
Now the mystery man behind the money giveaways can be revealed as Jason Buzi, a real estate investor who made millions from "flipping" homes.
Speaking to the Telegraph, 43-year-old Mr Buzi, who donates the money along with four of his friends, said he came up with the idea after his property business started making "serious money".
In a recent deal he made US$500,000 on a single house. He now plans to bring the scheme to London and then Birmingham before the end of the month.
• Tweeter sparks chaos, copycat in hunt for cash
Describing himself as coming from a "middle-class background, but by no means wealthy", he said he started looking for ways to make money at the age of 12, buying cookies for $1 from the local supermarket and selling them on for $3.
By the age of 19 he owned a car dealership. And by his mid-20s he was dealing in diamonds.
He made his fortune in the last four years from "flipping" houses - buying run-down properties below market price, increasing their value, and rapidly re-selling.
Most of his money "drops" have been in some of San Francisco and the surrounding Bay Area's poorest neighbourhoods.
Despite his good intentions, the property developer, from the Bay's Palo Alto himself, has faced criticism that giving away amounts of $100 or less trivialises the need of people in dire financial straits. And in particular as it is coming from someone who profited during the foreclosure crisis that crippled the region's housing market.
Local media, including SF Weekly, noted that he made his money from real estate "at a time when many people are struggling just to pay rent here" and that the drops will make little difference to those being priced out of the area.
"I'm totally mindful of that," he said. "I wasn't born wealthy. So many people I know have done better than me, and they're not doing anything to give back. So it's strange for someone who gives back to be criticised for how they give money."
He said the project was not meant as a business venture and he had never wanted the publicity. He was hoping to remain anonymous to enable him to carry on making the drops without being noticed.
Speculation in local media had been rife as to who could have been behind the generous donations, with guesses of everyone from Bill Gates to Mark Zuckerberg.
"My friends and I have laughed at descriptions of us being Donald Trump-type tycoons handing out presents like Santa Claus at Christmas," he said. "We're all just guys lucky enough to have made money in our work."
He calls his gifts an "anonymous social experiment for good" and has encouraged finders to share the money with those around them or do something worthy with their windfalls.
While he had had the idea for a while, his first drop was spontaneous and picked at random, he said, choosing a tourist spot near the city's Golden Gate Bridge while he was out with a friend who was visiting the city.
The others that followed were carefully chosen.
In Burbank, a suburb of Los Angeles, he watched from a nearby restaurant as hundreds gathered after he tweeted the clue: "Sounds like where a robin or eagle might keep their money."
"I was in the restaurant right by the spot I had left the money." he told the paper. "What I saw was incredible - hundreds of people outside searching. Some of the waiters even left to try to join the searchers."
At the biggest drop, where he left 37 envelopes hidden across a beach in LA, he sat watching the pandemonium as groups of friends, families and hordes of other hunters began digging.
Of the dozens of winners, he was particularly moved by 14-year-old Tatiana Ramierez, who cried after discovering $200 and said she would give the money to her sick grandmother in Mexico.
They have so far given away almost $10,000, and what had started as a small idea has now gone global, sparking copycats around the world.
The international reaction has encouraged the HiddenCash team to expand their scavenger hunts.
He told the paper their next stop after this weekend's giveaway in San Francisco would be London and then Birmingham before the end of the month.
"We're only going to get bigger," he said. "Let's hope the UK shares our sense of adventure."
New SF drop: find Mr. Franklin along the "crookedest street" (towards the bottom). Retweet when you find. pic.twitter.com/HDxbrfdh2X— Hidden Cash (@HiddenCash) May 27, 2014